Recent increase of the population of senior citizens has brought about the increased number of patients suffering from various functional disorders of the brain, typified by those accompanied by cerebral hemorrhage, cerebral infarction, subarachnoid hemorrhage, transient ischemic attack, cerebrovascular disorders, and the like. These disorders are considered to be caused mainly from the decreased blood flow in the brain, hypoxia in the blood, metabolism disorders such as hypoglycemia.
Most of conventional drugs for treating these disorders have paid attention to the causes of the disorders to be treated, and have focused on the treatment of sequelae of cerebral ischemia, cerebrovascular dementia and the like. Such conventional drugs include drugs for improving cerebral circulation, drugs for improving cerebral metabolism, drugs for improving cerebral functions, drugs for inhibiting the platelet coagulation, which have already been clinically utilized. Recently, irrespective of the causes of the disorders, cerebral protective drugs have been proposed and have attracted attention as a drug for treating cerebral function disorders. They are designed to eliminate cerebral function disorders or preventing the progress of the disorders by protecting the brain from ischemia or hypoxia.
These drugs for treating cerebral function disorders, however, have only insufficient clinical effects, and do not show clear cerebral protective action when tested on animals under a condition of single dose oral administration, though most of them are designed to be useful for oral administration.
Accordingly, cerebral protective drugs which promise excellent clinical effect and are useful for oral administration have still been desired.
Under the above circumstances, the present inventors have conducted careful studies to solve the mentioned problems, and have found that the novel diamine compounds of formula (I) and their acid addition salts exhibit an excellent cerebral protective action, and this action is securely obtained even in the oral route administration. This invention was accomplished based on the above findings.